JP2006506546A - Papermaking screen - Google Patents

Abstract

A paper machine sieve, consists of at least one single fabric for the paper side, and a single fabric for the running side, which consist of weft fibres (4,6) and chain fibres (1,5). The individual fabrics are joined together using binding fibres (3). The latter pass over the chain fibres at the points where the weft fibres pass underneath.

Description

  The present invention is a papermaking screen comprising at least one single fabric for the paper side and at least one single fabric for the machine side, each fabric comprising a set of weft and warp yarns, and At least a part of these stacked individual fabrics relates to a papermaking screen connected to each other by a binding thread.

  Today, in the paper industry, high performance paper machines operating at speeds up to 2000 m / min and with working widths exceeding 10 m are increasingly used. Very generally, the sheet forming unit is configured as a twin wire former (often as a gap former). It is typical of the paper machine that the sheet forming process occurs immediately in a relatively short dewatering zone between the two papermaking screens. The time for sheet formation is reduced to a few milliseconds due to this short distance and high discharge speed. The solids content or dry content of the fiber suspension must be increased from about 1 percent to about 20 percent during this time. This means that for papermaking screens, they must have a high dewatering capacity, but nevertheless leave no scar on the paper and provide a high fiber support.

  Another important point is the lateral stability of the screen tension, which is critical in determining the sheet thickness and moisture content profile. In modern machines operating with large sheet widths, very high requirements have been imposed precisely on this stability. Thus, to improve sheet formation, forming strips attached to and pressed against the machine side of the screen are increasingly being used in the sheet forming zone. This will result in a rapidly changing deflection of the screen fabric in the machine direction.

  In the state of the art, there are basically two different approaches for solving problems that meet these requirements and in particular for joining together the paper side and machine side fabrics. One solution is characterized in that these two individual fabric layers are connected together by weft yarns or weft yarns. Another solution is that the connection is effected by warps or warps. However, if it is desired to use different warp yarn diameters on the machine and paper sides, the approach as disclosed is now ultimately out of question.

  Thus, in order to reach a high stability value, when the configuration of the two individual fabrics is oriented, especially with the small diameter towards the fine paper side and the large diameter towards the coarse machine side. When oriented, these two layers must be connected by weft yarns, particularly bonded weft yarns. The current state of the art also makes corresponding proposals to solve this problem.

  Therefore, there is a possibility that the two individual cloths are stitched together by additional bonds or sutures that do not belong to the upper cloth (paper side) bond pattern or the lower cloth (machine side) bond pattern. Such a solution is disclosed, for example, in the papermaking screen of US Pat. No. 5,238,536, which provides a linen bond and a five-shank bond to the underlying fabric. Some approaches involve the joining of two fabric layers at the same time and in addition an additional suture that acts as a weft. Such a solution is disclosed, for example, in US Pat. No. 5,518,042.

  In such disclosed solutions, the additionally used binding yarn changes the inherently homogeneous upper side. In practical applications, this leads in part to undesirable scars on the paper. In order to counteract this result, the binding yarns are made increasingly thinner, but this has the disadvantage that the useful life of the connection of the individual fabric layers is correspondingly shortened. In addition, practical applications have shown that Alooping through @ of bonded wefts can occur, which will result in individual layer separation and render the fabric unusable.

  In another disclosed solution, the complete top weft yarn is replaced by a pair of bonded structural yarns. Depending on the type of fabric, the ratio of true upper weft or warp to combined weft pairs made with wefts will vary. For example, WO 99/06630 and WO 99/06632 disclose fabrics in which the top fabric is made as a type of linen combination by combining two combined weft yarns. In these disclosed solutions, the undercloth is now in the form of a five-shank combination.

  Despite the good interconnection of the two individual fabrics, the disclosed solution presents the essential disadvantage that the warp yarn on the paper side is not supported at the intersection of the joining weft yarns. If the Acomplete @ top weft weft is considered in these solutions, both yarns are placed at an elevated level as a result of the alternating combination of the top weft and the top warp, so that the warp and weft It can be seen that both bends are arranged in one plane. As a result of the use of bonded pairs, this support is now not at all intersections, and all yarns absorb main forces along their respective longitudinal axes that are oriented in the direction of the interior of the fabric at the intersections. To do. This disadvantage of lack of support occurs especially when the upper weft and the binding pair are introduced in an alternating order, for example a complete upper weft follows the binding pair and then the upper weft. In that case, in order to produce the linen conjugate disclosed as preferred, the subsequent upper weft yarn must extend over the warp yarn previously placed over the intersection, and as a result the warp yarn is a fabric. It is additionally pulled inside. The result is that every other warp is placed deeper in the fabric or the warp cannot be placed at the level of the weft. This leads to an uneven progression of the fabric on the paper side, i.e. it can lead to undesirable scars on the paper.

  Based on this state of the art, the object of the present invention is to avoid the drawbacks in the state of the art as described, and in particular characterized by a high stiffness value, in particular a high degree of lateral stability. It is to provide a papermaking screen that provides a dewatering output comparable to that of the disclosed solution and helps to prevent the formation of scars on the paper. The object as clearly stated in this way is achieved by a papermaking screen having exactly the features specified in claim 1.

  Thus, as specified in the characterizing part of claim 1, each binding yarn extends above the warp yarn of the individual fabric at a specific location on the paper side, and underneath at least one of this individual fabric. The weft yarn extends on the opposite side, and the connection of the two fabric layers (paper side and machine side) is also effected by the binding yarn, which is nevertheless sufficient in the fabric structure on the paper side. It is incorporated and supports the connection point by a special type of connection so that the connection yarn stays in one plane with the weft and the remaining warp in this way. Application of this bonding concept results in the production of a papermaking screen that has a high degree of rigidity, good dewaterability, and a uniform structure (especially on the paper side) to prevent undesirable scars on the paper. It will be.

  As a result of the solution claimed for the present invention, the warp is supported from below by the associated weft of the paper side individual fabric where the warp is pulled into the interior of the fabric by the binding yarn. The functional separation of the upper weft and the combined weft also allows a material (such as a polyester material) that supports the lateral stability of the fabric to be used for the upper weft (paper side), whereas In the above mentioned solution in the use of bonded weft pairs, both materials are of the same type and require optimization with respect to the layer connection (polyamide is conventionally used). Although only one binding thread is used in a given plane considered in the solution claimed for the present invention, the number of connection points and thus the upper and / or lower chains of the binding weft and the paper side and the machine side The contact between is not reduced compared to the disclosed solution.

  In one particularly preferred embodiment of the papermaking screen claimed for the present invention, the diameter of the binding yarn is defined to correspond to the diameter of the upper weft yarn, so that the high stiffness of the bonding of the fabric layers is achieved. Will be brought.

  Other advantageous embodiments of the papermaking screen claimed for the present invention are specified in the dependent claims. The papermaking screen claimed for the present invention is described in detail below with reference to the drawings, which are in schematic form not drawn to scale.

  In the state-of-the-art disclosure solution shown in FIG. 1, the papermaking screen as seen in line of sight with respect to FIG. 1 forms two pieces of fabric, ie, the upper piece of fabric or paper side. It consists of a cloth and an individual cloth or a lower cloth which is arranged underneath and forms the bottom side. The upper individual fabric consists of a set of a weft thread 2 as an upper weft thread and a warp thread 1 as an upper warp thread. The machine side located below also consists of a set of weft yarn 6 as the lower weft yarn and warp yarn 5 as the lower warp yarn. The disclosed solution has a linen bond as the bond type for the paper side and the lower fabric is configured as a five shank fabric for repeat. As shown in FIG. 1, the two pieces of fabric are connected to each other by a connecting weft thread 3, so that a plurality of such connecting weft threads (not shown) extend in and out of the plane of the drawing. Are thus arranged in sequence and thus the connection of the individual fabric layers necessary for the papermaking screen is achieved. In these disclosed solutions, the binding weft thread 3 is used in front of and beyond the upper weft thread 2 in the direction of the cloth to achieve the connection of the individual fabric layers, so that the paper side of the screen is actually very The upper side that is homogeneous is changed and disadvantageous so that unwanted scars can appear on the paper in practical applications. Thus, in order to be as disturbed as possible for the disclosed binding wefts 3, they are incrementally thinner, so that when the disclosed papermaking screen is used, the separation of the individual fabric layers and thus such As a result, the screen may be damaged.

  Thus, in the other disclosed solution shown in FIG. 2, two joint wefts 3 and 3 ′ are used, and their diameter is in particular the diameter of the disclosed joint weft 3 shown in FIG. Selected to be larger. As a result of the use of the two connecting wefts 3 and 3 ', in that case the full upper weft is no longer present at these locations. Rather, the upper linen bond is fulfilled by the union of the two bond threads 3, 3 '. In this example too, only a part of the papermaking screen is shown in cross-section, and a plurality of binding threads 3 and 3 'are present sequentially in different possible drawing planes. In this disclosed solution, a significant drawback can be seen in the fact that the warp yarn 1 is not supported at the intersection of the binding yarns 3 and 3 '. Even in this solution, irregularities on the paper side of the screen and thus also scars on the paper arise, because the linen bond is effected, so that the next on the warp yarn previously placed on the intersection This is because the upper weft thread must be extended and therefore further the warp thread is pulled into the interior of the fabric. Therefore, every other warp is either placed deeper in the fabric or the warp is not at the weft level, and this situation leads to the described drawbacks.

  The papermaking screen claimed for the present invention will now be described. For the sake of brevity and greater ease of understanding, the same reference numerals as for the disclosed solution described above will be used for the next illustration of the solution.

  A first exemplary embodiment of a papermaking screen as shown in FIGS. 3, 4 and 5 is provided with a linen bond on the paper side and configured as a five-shank bond on the lower or machine side. FIG. 3 is a top view of the upper or paper side section of the papermaking screen claimed for the present invention, and the section AA shown in FIG. 4 is presented as an illustration of an upper weft without a binding weft. Section BB, on the other hand, is an illustration of an upper weft with a combined weft as shown in FIG.

  In particular, FIG. 5 shows how the connection of two individual fabrics for the paper side and the machine side is achieved by the binding yarn 3. As an example, the progression of the binding yarn 3 is shown in the form of a cross-sectional view in FIG. This binding yarn is such that on the paper side, each binding yarn 3 extends over the associated warp yarn 1 of the individual fabric at a specific location, and at least one weft yarn 2 of this individual fabric is below these warp yarns 1 opposite the latter. In extending on the side, it is fully integrated into the fabric structure on the paper side. This extension up or down is indicated by reference numerals 7 and 8 in FIG. As a result of such an arrangement in which the associated connecting thread 3 extends above the warp thread 1 and the associated upper weft thread 2 extends below, the connecting point is supported from the opposite direction, so that this connecting point is connected to the other weft. And it is ensured that it stays on one plane with the warps 4 and 1. Accordingly, the upper weft thread 2 also extends uniformly at the place where the cloth is bonded without being bonded to the lower cloth. Only where the combined weft thread 3 extends over the upper warp thread is a short exchange of the upper weft thread 2 and the combined weft thread 3 performed. As a result, the warp yarns 1 arranged between them are viewed from below by the upper weft yarns 2 as seen in the line of sight to FIG. 5 where these yarns 1 are pulled into the interior of the fabric by the binding yarns 3. A contribution is also made to the support of the lower weft thread 6 by the supported and larger diameter warp threads 5, in particular the lower warp threads 5 (located below in the vertical direction of the warp thread 1, where the binding thread extends above and below). The

  As can also be seen in FIG. 5, each connecting weft thread 3 defines an angle with respect to the latter at the point of the associated extension 7 on the warp 1, but its size extends downwards at this point. Equal to the size of the weft thread 2. The magnitude of these angles is in the range of 90 ° to 130 ° in these areas as a function of the construction of the papermaking screen. As a result of these angular magnitudes, some sort of roofing board is produced both on the side of the upward extension 7 and at the point of the downward extension 8 in the opposite direction. This situation has a positive effect on the binding pattern and the overall pattern of papermaking screen forces.

  The coupling solution claimed for the present invention, configured as a five-shank combination with respect to repeats, is that the weft thread 6 extends below the four warp threads 5 and above the next warp thread 5 and up. It is defined that each joint weft 3 rises obliquely from the lower cloth to the upper cloth at the location of the extending portion 9. Each connecting weft thread 3 has a diameter essentially the same as the diameter of each weft thread 2 of the individual fabric on the paper side. In addition, the warp yarn 5 and the weft yarn 6 of the lower fabric (ie on the machine side) have a diameter that is larger than the diameter of the associated yarn system on the upper side of the papermaking screen, ie the paper side. With respect to the upper side of the screen, i.e. the paper side, the respective extension 7 on the respective binding yarn 3 is made up of three warp yarns 1 arranged between them, the three warp yarns 1 in the center of this group. The weft thread 3 is separated sequentially from the weft thread 2 and the connecting weft thread 3 extends downward 6 by a short distance in front of the upward extension 9 where the warp thread 5 is arranged below. As a result of the functional separation of the upper weft yarn 2 and the binding weft yarn 3 of the upper fabric, these two yarn sets can consist of different materials. For the purpose of increasing the lateral stability of the screen, preferably the upper weft thread 2 consists of a polyester material and the binding weft thread 3 consists of a polyamide material.

  The upper weft thread 4 shown in FIG. 4 corresponds in construction to the upper weft thread 2 with the joint weft thread 3 arranged upstream as shown. The differences in numbering were chosen solely for a better understanding of the top view of the fabric pattern shown in FIG.

  In the case of the modified embodiment shown in FIGS. 6, 7 and 8, this embodiment generally corresponds to the first embodiment described first, but in this case under 5 shanks. Instead of the side, a four-shank joint was used for the lower fabric or lower side (machine side). In each of the four shank joints shown in FIG. 8, the warp yarn 1 with the binding yarn 3 extending upward and the upper weft yarn 2 extending downward is now supported by the warp yarn 5 disposed below it of the lower fabric. And the lower weft thread 6 extends over the lower warp thread 5 at the point of support. In that case, the binding yarn 3 is tied to the lower fabric in the area of three consecutive warp yarns 5, so that the binding yarn 3 is above the central lower weft yarn 5 of two groups and two adjacent ones. It extends over the lower warp thread 5. The roof-like configuration in the region of the upward extension 7 for the upper warp yarn 1 has a configuration in the form of an extension 9 of the lower weft yarn 6 on the supported warp yarn 5 correspondingly parallel thereto.

  In the specific embodiment shown in FIG. 9, the order of the upper weft yarn 2 and the binding yarn 3 is changed, so that all the floating yarns of the warp yarn 1 have their connection points so that they are easily displaced towards each other. Despite being arranged, it has the same length L on the upper side. This ensures that the warp bends are arranged in one plane on the upper side in both the lateral and longitudinal directions. This has a positive effect in view of the slight possible scratching of the paper and the high degree of rigidity of the screen. A high degree of stability is achieved with the papermaking screen solution claimed for the present invention. The screen is characterized by a very good dewatering output and its production is cost effective.

FIG. 1 shows in cross-sectional form one coupling solution disclosed in the state of the art. FIG. 2 shows in cross-sectional form one coupling solution disclosed in the state of the art. FIG. 3 is a top view of the upper or paper side section of the papermaking screen claimed for the present invention. FIG. 4 is a cross-sectional view taken along line AA in FIG. FIG. 5 is a cross-sectional view taken along line BB in FIG. FIG. 6 is a top view of the upper or paper side of the second specific embodiment of the papermaking screen claimed for the present invention. 7 is a cross-sectional view taken along line CC in FIG. FIG. 8 is a cross-sectional view taken along line DD in FIG. FIG. 9 is a top view of the upper or paper side of a third exemplary embodiment that corresponds to the first exemplary embodiment but is implemented with an alternate weft sequence of upper and combined weft yarns.

Explanation of symbols

In addition, the following numerical identification is used in all of the illustrations.
1 Upper warp 2 Upper weft (with combined weft)
3, 3 'Combined weft thread 4 Upper weft thread 5 Lower warp thread 6 Lower weft thread 7 Upper extension 8 Lower extension 9 Upper extension by lower weft 6

Claims (9)

  A papermaking screen comprising at least one piece of fabric for the paper side and at least one piece of fabric for the machine side, each of these fabrics comprising a weft thread (4,6) and a warp thread (1,5) In a papermaking screen which is composed of a set and at least a part of the individual fabrics arranged one above the other are connected to each other by a binding yarn (3), each binding yarn (3) on the paper side is a warp of the individual fabric. (1) extending above (7) and at least one adjacent weft thread (2) of this fabric extending below these warps (1) on the opposite side of the fabric (8) Papermaking screen.   2. The papermaking screen according to claim 1, wherein exactly two individual fabrics are used as one upper fabric for the paper side and one as the lower fabric for the machine side to form the screen.   The papermaking screen according to claim 1 or 2, wherein only the first type of connecting wefts connects the individual fabrics as connecting wefts (3).   The top fabric is configured as a linen combination, and each combined weft thread (3) defines an angular magnitude relative to it at the point of extension (7) above the associated warp thread (1). 4. A papermaking screen according to claim 2 or 3, wherein is equal to the size of the correspondingly formed angle of the weft thread (2) extending downward.   The lower fabric is a multi-shank combination, in particular a four- or five-shank combination, with 3 or 4 warps (5) extending under the weft (6) of the lower fabric and one warp (5) below 5. A fabric according to any of claims 2 to 4, which extends over the fabric and each connecting weft thread (3) changes from a lower fabric to an upper fabric outside or at the location of such an upward extension (9). The papermaking screen according to one item.   6. A papermaking screen according to any one of the preceding claims, wherein each binding weft (3) has a diameter that is essentially the same as the diameter of each weft (2) of the individual fabric on the paper side.   From the upper part, the extension (7) above each binding thread (3) is supported by a warp thread (1) extending between the associated weft thread (2) of the upper fabric and that of the lower fabric. The papermaking screen according to any one of 6.   With respect to the weft thread (2), the extension (7) above each binding thread (3) is separated by three warps (1) placed between them, and the binding weft thread (3) is connected to three 8. A papermaking screen according to any one of claims 2 to 7, which extends under the lower warp yarn (5) of the lower fabric at the center warp yarn (1) of this group of weft yarns (3).   As a result of the functional separation of the upper weft thread (2) and the combined weft thread (3), the upper weft thread (preferably in order to increase the lateral stability of the screen, such thread is made of different materials. 9. A papermaking screen according to any one of claims 2 to 8, wherein 2) consists of a polyester material and the binding weft thread (3) consists of a polyamide material.

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